1. Field of the Invention
The present invention relates to an ink jet apparatus, and more particularly, to an ink jet recording apparatus employable for a printer, a facsimile, a copying machine or the like.
In a description below, a term. "recording" is used as a word which also includes "printing" of an image or the like on a paper, a texture or the like.
2. Description of the Related Art
In contrast with other types of printing systems, an ink jet printing system has advantages that a small-sized printing apparatus having a light weight can easily be realized on the actual machine basis, it generates little noise, and moreover, a printing operation can be performed with the apparatus using plain papers. For this reason, in recent years, most of low cost printers are designed and constructed to operate in accordance with a principle of the ink jet printing system. With a bubble jet printing system, i.e., one type of the ink jet printing system, a number of ink ejecting ports formed on an ink jet head can easily be arranged at a high density, and an ink jet printing apparatus having the bubble jet printing system employed therefor consumes a small quantity of electricity during each printing operation. In view of the foregoing fact, many printers each having the bubble jet printing system employed therefor are shipped to a commercial market.
At present, the ink jet printing system is classified into two types depending on a manner of supplying ink.
A first type of them is such that an ink jet head is mounted on a carriage, and a large volume ink tank is arranged at a predetermined position on the apparatus side so that ink is supplied to an ink jet head via an ink tube.
In the case that the above-mentioned type ink jet printing system is employed, each printing operation can be achieved at a very low running cost. However, since it is required that the running life of an ink jet head is substantially equal to or longer than that of an ink jet printing apparatus having the ink jet head mounted thereon, the structure of the ink jet head, associated component and materials employed therefor should be improved, resulting in a cost of the ink jet printing apparatus being unavoidably increased.
Secondly, there is known an ink jet printing system in which an ink jet unit consisting of an ink tank and an ink jet head is detachably mounted on a carriage.
In the case that the second-mentioned type ink jet printing system is employed, small extension of the ink tube is required, and an ink tank replacing operation can easily be achieved, and moreover, an ink jet printing apparatus having this ink jet printing system employed therefor can be constructed with small dimensions. However, when ink contained in the ink tank is consumed, the empty ink tank is replaced with a new one together with an ink jet head, resulting in a running cost of the ink jet printing apparatus being likewise increased. Especially, since the ink jet head having a running life at least until the ink contained in the ink tank is completely consumed should uselessly be wasted, the foregoing ink jet printing system is not acceptable from the viewpoint of ecology or a similar factor.
To eliminate the problems inherent to the last-mentioned type ink jet printing system, a proposal has been made with respect to an ink jet printing apparatus wherein an ink jet head and an ink tank are separately arranged and they are detachably mounted on a carriage as disclosed in Japanese Patent Application Laying-Open No. 4953/1988. The proposed ink jet printing apparatus has an advantage that the problem of an increased cost of the ink jet printing apparatus can be solved because the ink jet head and the ink tank can independently be replaced with new ones.
In the case that the ink jet unit is detachably mounted on the carriage, it is required that correct locating of the ink jet unit (the ink jet head and the ink tank) on the carriage and electrical connection between the ink jet unit and the main body side of the ink jet printing apparatus for transmitting signals to the former from the latter are taken into account. To satisfactorily meet the requirement, proposals have been made with respect to an improved ink jet printing apparatus as disclosed in Japanese Patent Application Laying-open Nos. 204342/1985 and 204343/1985. According to each of the prior arts, a plurality of electrical contacts for making electrical connection between an ink jet head and the main body side of an ink jet printing apparatus are arranged on the upper surface of the ink jet head located above an ink ejecting port, and moreover, other electrical contacts of the main body side of the ink jet printing apparatus are arranged on the carriage corresponding to the first-mentioned electrical contacts. To assure that the ink jet unit is correctly mounted at a predetermined position on the carriage, the ink jet printing apparatus is additionally provided with an engagement member.
With the ink jet printing apparatus constructed according to each of the prior art systems, however, since the ink jet unit is made of the ink jet head being integrated with an ink tank, the arrangement of the electrical contacts in the above-described manner is not necessarily acceptable in the case that modification is made so as to enable the ink tank to be separated from the ink jet head. In other words, in the ink jet unit with a structure such that the ink jet head and the ink tank are detachable from each other, on the ink jet head, there are disposed not only electrical contacts and a position determining member but also an ink supply portion for receiving ink from the ink tank. Therefore, the number of pieces of equipment to be provided for the ink jet head is increased. In addition, the arrangement of these pieces of equipment should be determined in consideration of an attaching/detaching operation to be performed when the ink tank is attached to and detached from the ink jet head and the connection structure of an ink path for supplying ink to the ink jet head. As a result, in the structure such that the attachment and detachment of the ink jet unit is performed relative to the carriage and such that the ink jet head and the ink tank which form the ink jet unit are detachable from each other, it has been requested that the following items are taken into account when the ink jet head and the ink jet unit are designed and constructed.
1) To prevent electrical reliability of the ink jet head from being deteriorated due to adhesive deposition of ink and paper particles on the ink jet head. PA0 2) To improve a positional accuracy of the ink jet head when the ink jet head and the ink tank are mounted on the carriage. PA0 3) To assure that the empty ink tank is easily replaced with a new one after the ink contained in it is consumed. PA0 4) To improve an accuracy of positional relation among plurality of ink jet heads when a color printing operation is performed using the plurality of ink jet heads. PA0 5) To easily produce ink jet heads, ink tanks and associated components.